The present invention relates to wireless communications. In particular, the present invention relates to a camera accessory for use with a mobile station in a wireless radiocommunication system.
The ability to conduct a telephone conversation while providing the participants with the ability to view each other is now and has been unquestionably desirable in a wide variety of situations. Advances in wireless telecommunications has made video phone communications more plausible as bandwidth increases and users demand an increasing array of features.
Prior art video phone technology exists, but has generally required expensive equipment and has required channels with wider than normal bandwidth. Providing video phone capabilities over standard telephone channels remains challenging due to the large amount of data generated by a typical image data channel. In order to provide realistic full motion live digital video, for example, it is generally accepted that at least 30 frames per second or the equivalent thereof be transmitted. A single uncompressed digital image having a typical frame size of 640xc3x97480 pixels and 3 colors components per pixel, e.g. RGB, requires a capability to process approximately 1 Megabyte of data per frame or roughly 30 Megabytes of data per second. Some systems use intraframe and interframe compression schemes to reduce the amount of data generated while preserving an effective 30 frames per second however, such systems often rely on motion based compression and are compromised when motion becomes excessive. In addition, such systems are often completely integrated and cannot interface with, for example, an external camera device.
Meanwhile, advances in modern digital cameras yields cameras equipped with extensive processing capabilities, capable of providing high quality high resolution digital images. Such cameras are typically equipped with high resolution color LCD displays, image processing circuitry and the like. However problems arise when expensive features associated with high end digital cameras are not needed, as when operating as an accessory in a telephonic system.
On the other end of the spectrum, a wide variety of simple CCD cameras exist which generate a raw video signal and may contain basic image processing such as, for example, frame grabbing or the like but fail to contain any further processing. One of the primary disadvantages associated with this type of system is that the processing required for practical image transfer on a limited channel resource, e.g. compression, encoding, decoding must be performed by the mobile terminal. Especially troublesome from a cost standpoint is the prospect of making the processing power available in the mobile terminal but having it remain unused if the user does not elect to use a camera.
In anticipation of an ever increasing demand for image transfer capabilities in the telephone network, some important standards have emerged. For example, the International Telecommunications Union (ITU) has developed a Common Intermediate Format (CIF) for image transfer as an optional part of the ITU-T""s H.261 and H.263 standards. CIF specifies 288 non-interlaced luminance lines, containing 352 pixels. CIF specifies frame rates of 7.5, 10, 15, or 30 per second. When providing CIF compliant video, the number of resulting bits cannot exceed 256 K bits (where K equals 1024). The following table provides a summary:
It should be noted that the ITU has been in existence since the 1800s and originated to standardize telegraphic communications and had traditionally be concerned with wired communications. Accordingly, the above standards were developed to facilitate the transfer of images over wired networks.
Modern wireless mobile terminals on the other hand are presently equipped with an increasing array of features and are incorporating better display technology to facilitate, for example, Internet accessibility. Simultaneously, as the ability to conduct, for example, video conferencing is enhanced by the emergence of the wireless Internet, no satisfactory prior art system is availably to allow widespread video conferencing or still image transfer from, for example, a mobile terminal.
Problems arise in that systems which provide video conferencing are generally expensive or fail to provide easy integration with existing mobile terminal hardware. In addition, such systems are bulky and diminish the portability related advantages provided by ever decreasing form factors associated with modern mobile terminals. Such a system is described in U.S. Pat. No. 5,550,754 to McNelley, et al. Therein a teleconferencing camcorder or telecamcorder is described wherein a video camera can produce images which can be recorded on a video tape or provided in a videoconferencing mode. The device can connect with a network and can display images on a built in display. McNelly""s device however suffers drawbacks including bulkiness and an abundance of features which are unnecessary. McNelly""s system further fails to fully develop compression concepts which are essential to modern digital image and video processing.
In U.S. Pat. No. 5,491,507 to Umezawa et al, video telephone equipment is described wherein a user may transmit and receive pictures and speech from a unit which can be held in one hand. A camera is permanently mounted to the casing which camera can alter its angle. However, Umezawa is directed primarily to packaging and fails to disclose detailed features, such as compression, involving the operation of the video telephone in a wireless radiocommunication system.
In still other systems, such as that described in Yuyama et al, where a portable compact imaging and displaying apparatus is provided, many features are integrated into a single unit or apparatus raising the costs associated with the unit. In addition, drawbacks exist in that it is not possible to use the camera section as an accessory and further limitations exist in providing, for example, compression features sufficient to allow ultimate transfer in a wireless radiocommunication system. Instead, Yuyama et al described how images may be transferred over a telephone line after establishing a connection using a conventional POTS style off-hook and connection sequence.
Thus, it can be seen that while digital cameras and even videophones exist and may be exploitable for teleconferencing and the like, the difficulty posed by, for example, providing a camera accessory to a mobile terminal in a wireless radiocommunication system remains unaddressed.
It would be appreciated in the art therefore for a method and apparatus for providing a camera accessory for a mobile terminal in a wireless radiocommunication system. Such a system could provide still and live motion video images over an air interface without the need for expensive digital cameras or videoconferencing systems.
It would further be appreciated in the art for a method and apparatus which would provide, for example, the ability to provide a camera accessory which would not require expensive display or battery technology.
To fulfill the needs of the art, a method and apparatus for providing a camera accessory including compression is described.
Thus in accordance with various exemplary embodiments of the present invention, a camera accessory is provided which camera accessory may be detachably coupled to a wireless mobile terminal associated with a wireless radiocommunication system. Such a detachable coupling may be by various means, such as, for example, mechanical attachments as will be described in greater detail hereinafter. The wireless mobile terminal may further include an image data interface and, as described, a physical or mechanical interface for detachably coupling the camera accessory thereto. Accordingly, one or more frames of image data may be captured in the camera accessory, for example, under control of the mobile terminal and thereafter compressed in the camera accessory, for example, by a compression block associated with a processor or the like, according to one or more compression formats. The captured frames and the compressed frames may be transferred to the wireless mobile terminal over the image data interface such that, for example, compressed image frames may be transferred further over an air interface while captured image frames may be displayed locally on the display associated with the mobile terminal. It should be noted that in order to reduce costs to the lowest possible level in accordance with the objective of the present invention, the camera accessory does not include a display.
In accordance with other exemplary embodiments of the present invention, the image data is captured in a predetermined format including, for example, a CIF format such as previously described, i.e. in a 352xc3x97288 pixel uncompressed format. The captured one or more frames may include a still image frame and accordingly, the one or more compression formats may includes a JPEG compression format for still image compression. JPEG compression preferably provides around a 25:1 compression ratio. The captured one or more frames may further include a stream of image frames and thus, the one or more compression formats includes an MPEG format. The captured one or more frames and the compressed one or more frames may further be transferred in one or more respective predetermined formats to the wireless mobile terminal over the image data interface. The one or more respective predetermined formats may includes, for example, an RGB CIF format, an YUV CIF format, a JPEG format, a MPEG format, and a MPEG-4 with CIF to QCIF conversion format. It should be noted that both compressed and uncompressed (CIF) image data may be transferred to the wireless mobile terminal, however, for transmission over an air interface, compressed data is preferable. It should further be noted that the image data interface may be a wired interface in which case the camera accessory derives power from a power supply located, for example, in wireless mobile terminal or may be a wireless interface in which case the camera accessory may be powered by a battery or the like or may derive power from an alternate source.